1. Field of the Invention
The present invention relates to a sensing device and a sensing system thereof, in particular to a fiber-optic localized plasmon resonance (FO-LPR) sensing device and a system thereof.
2. Description of the Related Art
At present, localized plasmon resonance (LPR) may be used to examine the change of local refractive index at the surface of noble metal nanoparticles, such that if there is a change of the LPR band, the spectral characterstics of an emergent light will be affected. If a suitable recognition unit is provided, its attachment onto a gold nanoparticle surface may be used to analyze a corresponding analyte in a sample, such that the local refractive index sensed by noble metal nanoparticles may be affected to achieve a specific sensing capability. If the noble metal nanoparticle layer (such as gold or silver nanoparticles) is disposed onto an optical fiber, the volume of the sensor may be reduced effectively, and the optical fiber may be used to enhance the variation of LPR signal through multiple total internal inflections, so as to improve the sensitivity of the sensor. In other words, the incident light signal is affected by LPR for each time of the light reflection, and a portion of the light energy is absorbed or scattered. Thus, the more the number of reflections, the greater is the attenuation of light intensity at that frequency, and the effect of enhancing the sensor sensitivity may be achieved. A sensing element developed by the aforementioned optical fiber and the principle of LPR is called a fiber-optic localized plasmon resonance (FO-LPR) sensor. The FO-LPR sensor concurrently has a high sensitivity and selectivity after it is integrated with recognition molecules, and thus the FO-LPR sensor has a high potential to be developed as a chemical and biochemical sensor. In addition, the method of enhancing signals with multiple total internal reflections may be applied to the technology of measuring a surface-enhanced spectrum such as surface-enhanced Raman scattering and surface-enhanced fluorescence.
Although the FO-LPR is highly sensitive and specific and has the real-time detection capability, the sensor must be exposed to a complicated matrix if a real sample is sensed. For example, cell debris, blood cells, and immune cells or even a suspended matter such as dusts and fibers will be attached or deposited onto a surface of the sensor easily, so that the noble metal nanoparticles will have a change of local refractive index at their surfaces caused by the aforementioned surface covering process, so as to produce a serious error of measurement. Therefore, it is necessary to eliminate the non-specific attachment of such large particulate substances in order to use the FO-LPR for sensing an analyte in a real sample.